The present invention relates to a heat pump type air conditioning and heating system for use in vehicles, such as passenger cars and trucks. More specifically, the present invention relates to a heat pump system for use in vehicles having a fuel cell available as a source of waste heat.
Heat pump type air conditioning and heating systems use a refrigerant that is capable of absorbing and radiating heat energy. A compressor applies a work load to the refrigerant by pressurizing it, and forces the refrigerant through a series of interconnected heat exchangers. In each heat exchanger, the refrigerant either absorbs or radiates heat energy, thereby cooling or heating a surrounding medium, such as air within a passenger cabin of a vehicle.
Prior heat pump type systems utilized ambient air to provide the waste heat necessary to further the heating and cooling cycle of the refrigerant. Due to this arrangement, these systems typically perform poorly at low ambient temperatures due to ineffective transmission of heat by the cold air. Furthermore, ice may form on the heat exchanger, reducing air flow and consequently reducing the efficiency of the system. Also, these systems cannot operate sufficiently in the absence of a relatively large source of waste heat, a problem that arises in vehicles that lack traditional engines, such as vehicles that utilize solar energy, fuel cells, and/or hybrid engine configurations.
The use of fuel cells and hybrid electric engine configurations is becoming increasingly popular in modern motor vehicles. Typically, these systems include one or more coolant circuits that serve to cool the various electronic components of the systems.
The present invention provides a heat pump type heating and/or air-conditioning system for a vehicle. The system utilizes external coolant circuits in a heat exchange relationship with a refrigerant to provide the necessary transfer of heat energy that allows the circuit to operate. In a preferred embodiment, the heat pump system comprises an external fuel cell coolant circuit and an internal refrigeration circuit. The fuel cell coolant circuit includes an external evaporator and the refrigeration circuit includes an internal condenser. The external evaporator defines a heat exchange relationship between the refrigerant of the refrigeration circuit and coolant of the fuel cell coolant circuit. This relationship allows the refrigeration circuit to gather waste heat from the fuel cell coolant circuit. Also, the internal condenser defines a heat exchange relationship between the refrigerant and the air within the vehicle. This relationship allows the refrigeration circuit to utilize the energy gathered from the fuel cell circuit to transfer heat energy to the air of the vehicle.
Preferably, the refrigeration circuit also includes an internal evaporator and the heat pump system also includes an external electronics coolant circuit. The electronics coolant circuit includes an external condenser that defines a heat exchange relationship between the electronics coolant and the refrigerant. This relationship allows the refrigeration circuit to dump heat into the electronics coolant circuit. Also, the internal evaporator defines a second heat exchange relationship between the refrigerant and the air within the vehicle. This relationship provides a point at which the refrigeration circuit can transfer heat energy from the air of the vehicle. Preferably, the heat pump system further includes a multiposition valve that selectively allows refrigerant to travel to either the internal condenser or the external condenser, thereby allowing a user to select between heating and air-conditioning modes.
The present invention also preferably includes an arrangement that allows for a dehumidification operation. In this embodiment, the heat pump system includes a junction passageway that allows refrigerant to flow through both the internal and external condenser and the internal evaporator, which allows the air of the vehicle to be cooled prior to heating.
The present invention also provides a method of selectively heating or cooling air within a passenger compartment of a vehicle. The method comprises gathering waste heat from an external coolant, such as a fuel cell coolant, transferring heat energy from the waste heat to a refrigerant, transferring heat energy between the refrigerant and a second coolant, such as an electronics coolant, and ultimately transferring heat energy between the refrigerant and the air within the vehicle.